New research suggests road decommissioning important for grizzly bears

Grizzly bears are on the decline in Alberta, Canada.  Human-caused mortality such as over-hunting, poaching, and collisions with vehicles have dramatically reduced this population in recent years.  While the decline of bears has resulted in a suspension of hunting of grizzlies in the province, other sources of mortality due to access continue to threaten grizzly bear persistence. 

A new study published in the journal, Biological Conservation, found that road decommissioning may be necessary to ensure grizzly bear survival in southern Canada.  Nielsen et al. (2008) modeled different timber harvest scenarios impact on grizzly bear long-term survival.  While logging and the creation of early-successional forests could benefit habitat quality and lead to increased carrying capacity, the associated road building and human-caused mortality would offset any habitat gains.  They suggest that, “to minimize immediate risk of population decline, areas should be identified or prioritized for habitat restoration through road decommissioning.”  In conclusion they state, “For grizzly bears, the spatial configuration of forest harvesting is a red herring.  Road development, access management, and human attitudes are far more important factors to Alberta grizzly bear populations than the shape and size of clear-cuts.”

Check out the abstract below.  You can find the full article at your local library or purchase it online at:  http://www.science-direct.com/science/journal/00063207


Nielsen, S.E., G.B. Stenhouse, H.L. Beyer, F. Huettmann, AND M.S. Boyce.  2008.  Can natural disturbance-based forestry rescue a declining population of grizzly bears?  Biological Conservation 141: 2193-2207.  

Forest managers are increasingly considering historic patterns of natural forest disturbance as a model for forest harvesting and as a coarse-filter ecosystem management tool. We evaluated the long-term (100-year) persistence of a grizzly bear population in Alberta, Canada using forest simulations and habitat modeling. Even with harvesting the same volume of timber, natural disturbance-based forestry resulted in a larger human footprint than traditional two-pass forestry with road densities reaching 1.39 km/km2 or more than three times baseline conditions and suggested maximum levels of security for grizzly bears. Because bears favour young forests and edges where food resources are plentiful, a future shift to young forests and more edge habitat resulted in a 20% projected increase in habitat quality and a 10% projected increase in potential carrying capacity. Human-caused mortality risk, however, offset any projected gains in habitat and carrying capacity resulting in the loss of all secure, unprotected territories, regardless of forest harvest method, within the first 20–30 years of simulation. We suggest that natural disturbance-based forestry is an ill-suited management tool for sustaining declining populations of grizzly bears. A management model that explicitly considers road access is more likely to improve grizzly bear population persistence than changing the size of clear-cuts. In fact, large clear cuts might be counter productive for bears since a diversity of habitats within each bear’s home range is more likely to buffer against future uncertainties.